Entropy-Based Channel Access Control for S-ALOHA in Wireless Ad-Hoc Networks

In this paper we present a novel cross-layer medium access control scheme that uses information about the network topology in order to select the adequate transmission probability at the individual nodes. In the proposed Entropy-based Medium Acess Control protocol (EbMAC), the probability of accessing the channel of each node is a function of the topological network entropy and their individual probability of being selected as relay in an end-to-end path computed by the routing algorithm. The topological network entropy measures the ability of the network to distribute the data traffic among the nodes. High values of network entropy indicate that the data trac will tend to concentrate around particular regions of the network and hence, that these regions are more likely to experience contention. In this case, the channel access probability has to be selected in such a way as to reduce the packet collision probability in such hot spots. Simulation-based experiments show that the proposed scheme attains performance gains in terms of throughput, collisions ratio and end-to-end delay.